Hydrogen penetration into the NiTi superelastic alloy investigated in-situ by synchrotron diffraction experiments

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Authors

  • Tomas Zalezak
  • Milan Jary
  • Ondrej Zobac
  • Jan Mrazek
  • Jan Frenzel
  • Jozef Keckes
  • Antonin Dlouhý

External Organisational units

  • Institute of Physics of Materials ASCR
  • Faculty of Science
  • Ruhr-Universität Bochum

Abstract

Microstructural changes induced by a hydrogen permeation into the NiTi superelastic alloy were investigated in-situ using the X-ray synchrotron diffraction. A new design of an electrochemical cell enabled to uncover time and position dependent processes under a flat alloy surface exposed to the cathodic hydrogen. The diffraction data supported by thermo-elastic FEM calculations helped to quantify an evolution of compressive stresses in the B2 austenitic phase hosting hydrogen atoms. The compressive stress state initiates a formation of martensitic phases starting from the exposed surface layer and advancing into the alloy volume with increasing time of hydrogen charging. We have performed the ab-initio DFT study in order to rationalize volumetric changes associated with variations in the B2 austenite and B19′ martensite lattice parameters. The numerical results also contributed to the identification of a new hydride phase with orthorhombic crystal structure and lattice parameters a = 0.8505 nm, b = 0.7366 nm and c = 0.4722 nm.

Details

Original languageEnglish
Article number120217
Number of pages11
JournalActa materialia
Volume277.2024
Issue number15 September
DOIs
Publication statusPublished - 23 Jul 2024